Devices and Methods for Determining Heart Function of a Living Subject

ABSTRACT

The present invention relates to systems, methods and algorithms for determination of heart pump function and their use in livings subject are described.The invention further relates to complementary parts of such systems that work best in combination.Medical catheters, sheaths and shafts are disclosed that carry an arrangement of integrated digital sensor systems-on-chip (SoC) in the portion thereof residing inside the body. These devices combine at their portion that resides inside the body, the complete chain of signal transduction, signal analog-to-digital conversion and digital signal transmission, and allow to acquire single and multiple physical entities in a single setup. In specific instances the devices integrate wireless data transfer functionality, and in specific instances they integrate wireless energy harvesting for battery-free functionality.The present invention further describes complementary monitor systems that are suited for reception, processing and analysis of data acquired by such catheters/sheaths/shafts to yield a robust assessment of cardiac performance.Moreover, the present invention relates to innovations which render such systems applicable to patients with and without cardiac assist devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.16/479,438, filed Jul. 19, 2019, which is a U.S. National Phase of, andApplicant claims priority from, International Application No.PCT/EP2018/051255, filed on 19 Jan. 2018, and European PatentApplication No. 17152103.2, filed on 19 Jan. 2017, both of which areincorporated herein by reference in their entirety.

BACKGROUND

Pump action of the heart is a fundamental vital function of the body andits accurate determination is important in many disease states, insports and in other application fields. The determination of cardiacoutput, defined as the integrated forward flow of blood from the leftventricle over a time interval, correlates in a very nonlinear fashionwith various measurable biological parameters. This correlation isfurther influenced by the presence and activity of artificial devices,e.g. heart assist pumps, in various locations of the circulatory system.There are a number of clinical measurement techniques of heart pumpfunction, including cardiac catheterization, thermodilution and pulsewaveform analysis, but all methods have specific limitations, includinginaccuracy, ineffectiveness, invasiveness, and practical difficulties intheir clinical application.

Need for New Catheters

Determining and monitoring of the performance of the heart, inparticular cardiac output, often relies on assessment of a single, keyphysiologic parameter that is taken as surrogate forthe—inaccessible—cardiac output parameter of interest.

Typically, measurement of parameters for computing cardiac output (CO)rely on invasive catheters. Such catheters often contain either a fluidline that propagates the pressure inside the body to a sensor outsidethe body, or it consists of optical line that propagates a light signalfrom a measurement location inside the body to a sensor outside thebody, or it contains an electric line that transports an analog signalfrom inside the body e.g. from a thermistor, to an analog-to-digitalconverter outside the body. The transmission of physical or analogsignals from inside the body to a transducer outside the body issusceptible to mechanical or electrical noise; such catheters are oftendifficult and expensive to manufacture; their handling in clinicalpractice is laborious; the multiple connections (analog wires, fluids)and the external power supply and signal transfer lines that are neededfor functionality render patient management more complex.

Future systems for cardiac output determination should thereforeinnovate in catheter designs to overcome these limitations.

Using a single parameter for determination of cardiac output, as istypically done with thermodilution or pulse contour analysis, hasseveral disadvantages:

1) the surrogate parameter may not accurately represent the required butinaccessible heart function parameter;

2) surrogate values may be confounded by other physiologic and technicalparameters;

3) the reliance on a single sensor renders the method sensitive tosensor errors including noise, drift, sensor inaccuracy, sensordisplacement; and

4) cardiac assist systems, be they implanted, external, or based onpercutaneous catheters, are typically major confounders of currentlyused algorithms for computing cardiac output (CO).

Need for Multiple Parameters and their Integrated Analysis

In contrast, heart function determination methods that are based oncombination of multiple biological signals have the potential toovercome weaknesses mentioned, in part by delivering more robust primarysignals and by allowing control of confounding factors. One importantpractical limitation of current clinical practice when monitoringmultiple vital parameters is that this leads to increased complexity ofpatient management, because each additional sensor typically comes withits own cable for power supply and sensor signal output, therebyincreasing complexity and cost.

Thus, future systems for cardiac output determination should preferablyhave the capability of a) acquiring multiple signal modalities, with aminimum amount of equipment, in synchronous fashion, b) analysing suchmultiple signal parameters in combination, and c) being applicable andreliable in patients that receive mechanical circulatory support. Thisimplies the need for innovation in cardiac monitor devices andalgorithms to be used in conjunction with catheters/sheaths/shafts inthis invention.

PRIOR ART

Most current state-of-the art monitoring catheters are capable ofprobing a single physical modality inside the body, that in typicalscenarios is guided to the outside of the body where an externaltransducer converts the physical signal to an analog signal and theanalog signal is converted in an additional stage to a digital signal,the typical example being current invasive pressure monitor catheters.

In addition, there exist medical pressure wires that can be placed inthe body to measure a single signal that transduce pressure at the wiretip by converting it to an analog signal inside the body, and guide theanalog signal to a catheter portion outside the body, with the deviceneeding to be connected to a second device (the interface box) outsidethe body for analog to digital signal conversion and data transmission(Radi Patent 1997, see http://patents.justia.com/patents/6112598),(Volcano patent 2002, see http://patents.justia.com/patent/6976965).There exist medical Doppler wires that allow to extract a singleultrasound Doppler signal from the body, by reading out not only lowfrequency pressure but also high frequency pressure oscillation througha similar catheter; also in this case, an analog signal is guided fromthe catheter tip to a location outside the body where additionalequipment is required for analog to digital conversion (Volcano patent2002, see http://patents.justia.com/patent/6976965). In addition, alimited number of multimodal sensing catheters for medicine exists, thattypically have an analog sensing element and a number of channels offibers that guide a physical signal (pressure, light) out of the body tobe transduced to an electrical signal outside the body. An example isthe CCOmbo/SvO2 pulmonary artery catheter from Edwards Life Science. Itcombines an analog temperature sensing thermistor at its tip inside thebody, contains fluid filled lumina that allow pressure determinationoutside the body by an added external pressure transducers, and opticalfibers that guide an optical spectrum to outside the body, whereby theactual optical sensors transduce the physical signal into a stream ofdigital information are located outside the body.

Prior Art in Monitors for Computing Cardiac Output

The main methods employed currently are the pulmonary artery catheterand in the PiCCO system and the pulmonary form the main body of priorart.

a) Pulmonary Artery Catheter in Detail: Pulmonary artery catheters werelong considered the mainstay of cardiac output monitoring in clinicalpractice, although it is well known that they are not accurate invarious circumstances. The simplest pulmonary artery catheters measure atemperature curve in the pulmonary artery after injection of cold fluidinto the right atrium. They are often difficult to place, have a risk ofinfection and of pulmonary artery damage, and a large measurementvariability, in particular when tricuspid (heart) valve insufficiency ispresent, like in most severely sick individuals. The alternative Fickmethod for cardiac output determination relies on the oxygen content inblood drawn from the pulmonary artery drawn by the pulmonary arterycatheter, and in the arterial circulation. As this method relies on theknowledge of total body oxygen consumption (which is typically alteredin sick individuals), it is unreliable. Yet another method is continuousmonitoring of central venous oxygen saturation by optical fiber-equippedcatheters. Because this parameters depends on many confounders unrelatedto cardiac output, it is not considered as good surrogate of cardiacoutput. All these mentioned pulmonary artery catheter based methods areold with multiple expired patents covering them.

b) PiCCO system in detail: The PiCCO system relies on bolusthermodilution measurement in a central artery after injection of a coldfluid bolus injected into a central vein, thus needing two separate,central vascular catheters. Technically, it consists of a thermistor ona tip of a catheter with an external signal digitizer and datatransmission in a separate, external module. In addition, PiCCO can usethe blood pressure contour guided out from a central artery through afluid filled lumen to be monitored using an external pressure transducerfollowed by an external analog-to-digital converter and datatransmission.

c) HighDim prior art (U.S. patent application Ser. No. 13/827,063)describes an apparatus and methods to compute cardiac output based onmultiparameter physiologic data that are analyzed using multidimensionalnonlinear optimization to compute cardiac output. A limitation of thismethod is that it does not account for the case when a circulationassist device, e.g., an implantable cardiac pump, contributes to thecardiac output of the individual. In such a case, the true cardiacoutput is underestimated because the machine contribution is notaccounted for; in addition, the implantable cardiac pump will inducechanges in the circulatory system that are unaccounted for in thealgorithm learning process described in U.S. patent application Ser. No.13/827,063.

Improvements in medical monitoring technology is desirable because theycan lead to improved patient management.

Measuring multiple physical signals at a location inside the body hasthe potential to yield information that is suited as input to algorithmsand systems that can exploit the complementary, redundant, and mutuallydependent information content of signals, as described below.

Definition of Terms

By the expression “inside the body” any configuration is herebyencompassed wherein a medical invasive device is, in total or limitedlyto just a body portion thereof, inserted into one of a blood vessel, abody cavity and a body tissue.

With Catheter, a hollow tube of a diameter less than a centimetre andmore than hundred micrometer is meant that has a primary function toconnect a body compartment, typically the intravascular compartment,with the outside of the body for with the goal of one of, infusion oftherapeutic liquids, withdrawing blood, and measuring the hydrostaticpressure through a water column guided to the outside of the body.

With Sheath, a hollow tube of a diameter of less than a centimetre andmore than 100 micrometers is meant that serves to contain in its mainlumen an elongated inner object and guides it from the outside of thebody to inside the body. Such a sheath may contain zero or moreadditional hollow lumina for other purposes, in addition to theobject-carrying main lumen.

With Shaft, an elongated object with a diameter of less than acentimetre and more than 100 micrometers is meant that has the primaryfunction to carry on its part inside the body a number of functionalsubsystems that includes at least one of, a pump, and a sensor array.C/S/S is here used for “catheters, sheaths, shafts”.

Miniaturized digital sensor System-On-Chips (SoC) as described herecombine, in integrated package having a diameter measured perpendicularto a device axis, not larger than the available space at target locationinside the body, (typically smaller than 5 square millimeters forcatheters and shafts arranged for diagnostic purposes only, andtypically smaller than 20 square millimetres for sheaths that are usedin conjunction with heart pumps), the necessary circuits to yield adigital encoding of a quantitative measurement of a physical modality,including at least the signal to analog transduction, analog-to-digitalconversion, and digital transmission. The use of such miniaturizeddigital sensors has the following advantage: a) the transmission ofanalog signals, which is prone to noise and bias, is eliminated: b) thenumber of noise sources is reduced because of integrated transducing anddigitizing sensor elements; c) digital multiplexing of the output ofmultiple sensors allows minimizing the number of signal lines; d) themanufacture of the (C/S/S) is simplified because fewer electricalconnections are needed, and e) digital sensors with very low powerrequirements exist. The size limit of those sensors is important becauseclinically tolerable access size to blood vessels is limited andtypically ranges up to from 0.5 to 3 millimeter device diameter forpurely diagnostic use, up to 5 mm for shafts of circulation assistdevices, and up to 8 mm for catheters used in extracorporealcirculation. Power requirements of sensors are important for clinicalapplication and are preferably low, to simplify power supply and avoidexcessive heating of the sensor that is clinically undesirable.

Computer

In connection with the invention the term “computer” can relate to anysuitable computing system. In particular, the computer can be a desktopcomputer, a laptop computer, a tablet a smartphone or a similar deviceas well as an embedded computing system such as a microcontroller or anyother single- or multi-processor embedded system.

Energy Harvesting

Energy harvesting is used to designate a process whereby a deviceextracts electrical energy from a physical energy source in itssurroundings without having a wired connection to the energy source.Energy harvesting technology is well known to a practitioner in thefield. In the context of this patent, the term coil designates anelectrical coil.

Heart Pump

A heart pump is defined as a medical device that pumps blood from onecompartment of the blood circulation to another compartment of the bloodcirculation. Typical pumps include: a) extracorporeal pumps that have amechanical pump part outside the body; b) catheter-based pumps that havethe mechanical pump part inside the body and are mounted on the tip of ashaft that crosses the skin; and c) fully implantable pumps that havethe mechanical pump part inside the body and no part except a powersupply cable that crosses the skin.

Deep Neural Network

In machine learning field, a deep neural network (DNN) is an artificialneural network (ANN) with multiple hidden layers of units between theinput and output layers.

Deep Believe Network

In machine learning field, a deep believe network is a type of a deepneural network, comprising multiple layers of latent variables withconnections between the layers but not between units within each layer.

SUMMARY

According to the present invention, the need for more precise measuringof signals which reflect the heart performance of a patient and allowthe extraction of cardiac output parameters better representing thecardiac output is settled by a medical invasive device; a method ofcomputing cardiac output and apparatus as it is defined by the featuresof the respective independent claims Preferred embodiments are subjectof the dependent claims.

In particular, the present invention deals with an innovativeconfiguration for medical invasive devices wherein, for instance, signaltransduction, analog-to-digital signal conversion and digital signaltransmission are moved into the portion of the catheter arranged to belocated inside a vessel lumen, by using miniaturized digital sensorSoCs. Accordingly, medical digital sensor SoC arrays are mounted oncatheters, sheaths and shafts at their location inside the body.

The advantages deriving from such innovative configurations comprise 1)reducing or eliminating the need for signal transducer modules outsideof the body, thus simplifying industrial production, distribution andclinical use, and 2) the elimination of hydrostatic columns for pressurepropagation, of wires carrying sensitive analog signals and of opticallines for signal transmission. The proposed setup consists of devices inthe shape of (C/S/S) that comprise miniaturized digital sensors at theirtips performing the stages of physical signal sensing, signaltransduction, analog-to-digital signal conversion and digital signaltransmission, at a location positioned inside the body.

Moreover, a multitude of sensor SoCs that measure different,complementary physical signals, can be placed into a portion of amedical (C/S/S) arranged to be positioned inside the body, according tothe present invention.

Sensors to be used in connection with the present invention aredescribed below more in detail.

In line with the above innovative configuration, an arrangement ofmedical digital sensor SoC and SoC arrays is provided wherein thesensors are mounted at the portion of a medical invasive device that islocated inside the body. Integrated multimodal sensor arrays for vitalbiosignal monitoring can be thus integrated in one of:

-   -   a) the shaft of a circulatory assist device;    -   b) a free standing shaft;    -   c) a vascular access sheath; and    -   d) a intravascular catheter.

A number of useful sensor combinations are possible and below given asnon-limiting examples.

The integration has the advantage of reducing the number of accesscables to a patient to one per sensor array and leads to improvedpracticability in a clinical scenario.

In addition to that, in the following devices are described in the shapeof a medical (C/S/S) comprising an arrangement of digital sensor SoCswith digital transmission at a location arranged to be positioned insidethe body, that incorporate a digital interface at their part arranged tobe located outside the body to allow to connect a connector cable forpower supply and digital data transfer.

While the embodiments conceived according to the above aspect of theinvention already simplify and improve medical monitoring, it is stilldesirable to also give up wired power supply and communication. Forthese reasons, further improvements are desirable.

According to another aspect of the present invention, wirelesstransmitting catheters and/or sheaths and/or shafts can be designed withintegrated Medical Sensor SoCs and SoC arrays. Accordingly, anintegrated multimodal biomedical sensor array may be driven by anintegrated battery and read out by wireless data transmission.

Accordingly, a further aspect of the present invention consists of amedical (C/S/S) with an arrangement of miniaturized digital sensor SoCsat their portion arranged to be located inside the body in combinationwith a wireless communication chip and a miniaturized battery located atthe portion arranged to be located outside the body in a singleembodiment. This allows to eliminate the need for cables for powersupply and communication and may greatly improve clinicalpracticability. It will also improve electrical safety because nometallic connection to the patient is needed.

According to a further possible embodiment of the present invention, amedical (C/S/S) can be designed with an arrangement of miniaturizeddigital sensors arranged to be located inside the body and a connectorin combination with a pluggable module that comprises a small batteryand electronics for wireless signal transmission.

This has the advantage that an empty battery can be replaced by pluggingin a charged replacement module.

From the large spectrum of potential sensor modalities that can be usedas elements for the sensor array according to the present invention, thefollowing are preferred:

-   -   miniaturized digital pressure sensor SoCs are beneficial,        because they allow to measure the blood pressure (an important        parameter of cardiac function) at given locations but in        contrast to conventional sensors neither require the        fluid-filled pressurized access channels nor the extracorporeal        transducers that are typically used in conventional pressure        monitoring catheters, and do not rely on analog signal        transmission along the device. A preferred example of a        miniaturized digital temperature sensors are beneficial because        they allow to monitor body temperature and also because they        allow to measure temperature fluctuations that occur after        injection of boli of cool fluids; the character and timing of        such temperature fluctuation after such thermal bolus injection        are related to cardiac performance.    -   miniaturized digital light emitters and receivers for multiple        wavelengths allow determining the spectral components of the        blood and thus derive blood oxygenation using standard formulas;        it is well known that blood oxygenation and its time course        contains relevant information about cardiopulmonary function.    -   miniaturized digital vibration sensors allow sensing the        dynamic, turbulent aspects of blood flow and may thereby        contribute information to cardiac function.    -   ultrasonic Doppler sensors allow to measure blood flow velocity        and thereby contribute information cardiac function.    -   direct ultrasonic flow sensors allow to determine wave velocity        between two points and thereby to measure blood flow velocity        directly, contributing information about cardiac function.    -   voltage sensor: allows direct detection of electrical heart        action timing and frequency; allows measurement of local body        impedance.

While the above ameliorations over the prior art improve patientmanagement, the elimination of the need for a battery is still desirablebecause it has the potential to simplify manufacture, to improve shelflife, to reduce cost, and to reduce the risk of battery leakage. Furtherinnovations are therefore desirable.

In a further aspect of the present invention, a device in the shape of amedical (C/S/S) comprising an arrangement of digital sensor SoCs attheir portion arranged to be located inside the body with a wirelesstransmission electronics in one of, their portion arranged to be locatedoutside the body and a pluggable module, is additionally equipped withan energy transfer and harvesting mechanism that allows to eliminate theneed for a power supply through battery or cable. A battery-free, energyharvesting medical sensor array, in combination with catheters, sheathsand carrying shafts, is described. Independence of batteries can lead tomore compact designs and to improved practicability because batterydischarge is not an issue anymore.

Recent progress in wireless technology has made it possible to producewireless sensors, which can be battery driven, thus reducing the needfor cables.

Recent progress in energy harvesting has made it possible to harvestenergy from environmental sources, like electromagnetic fields,sunlight, vibration, heat, etc.

The following energy harvesting mechanisms can be used: a) inductiveenergy transmission through electromagnetic fields; b) capacitive energytransmission; c) solar-cell based energy transmission; d) vibrationbased energy harvesting and d) thermoelectric energy transduction. Apreferred version is the inductive energy transmission because largerenergies can typically be transferred compared to other setups, but highvoltages on the energy transmitter side are not required.

Furthermore, the present invention deals with algorithms for combiningvital signals with technical control signals and motor parameters. Itdiscloses a novel combination where multiparameter biosignal monitoringas known in the state of the art is combined with technical controlsignals and performance signals originating from a catheter-based orimplantable circulatory pump, thus going beyond the state of the art.This has the practical advantage of rendering the biosignal analysisapplicable to patients who have a catheter-based or implantedcirculatory assist device.

The present invention also deals with methods to be used in conjunctionwith multiparameter signals that are suited for patients with andwithout heart assist devices.

One method combines a number of physiologic data sources with a numberof parameters derived from a heart assist device and builds a non-linearmathematical model that correlates those data to targeted cardiac outputvalues. The physiologic data vectors include one or more measurable orderivable parameters such as: systolic and diastolic pressure, pulsepressure, beat-to-beat interval, mean arterial pressure, maximal slopeof the pressure rise during systole, the area under systolic part of thepulse pressure wave, gender (male or female), age, height, weight, anddiagnostic class. The parameters derived from a heart assist deviceinclude one or more of the following: device blood flow, device type,device performance setting, motor current, rotation frequency, pressureinside device, pressure across device. The target cardiac output valuesare acquired using various methods, across a plurality of individuals.Multidimensional nonlinear optimization is then used to find amathematical model which transforms the source data to the target COdata. The model is then applied to an individual by acquiringphysiologic data for the individual and applying the model to thecollected data.

A step consists of adding heart assist device parameters in addition tothe physiological parameters for building a model. In contrast to whatwas done in prior art, this invention uses the joint information ofbiology and assist device to achieve a more robust result. Using setupsdescribed in prior art, assist device acted as confounders, while in thecurrent invention the machine parameters are now sources of usefulinformation. Practically, this will expand the patient spectrum to whichsuch monitoring can be applied.

In another embodiment, measurements of the same biological parameter(preferably blood pressure and its time course) is performed at twodifferent locations in the same compartment of the circulation. Theadvantage of this approach is that pulse wave propagation, that is ahighly nonlinear biologic process, goes into the mathematical model asadditional information and has thereby the potential to render themathematical model more robust. In contrast, neglecting the pulse wavepropagation as done in usual clinical practice renders wave propagationof the pulse wave a confounding factor for cardiac output analyses.

The present invention furthermore discloses a monitor designed forallowing the above described determination of a cardiac performancebased on combinations of medical signals and motor control/performancesignals; as well as:

-   -   a system for monitoring vital signs based on combinations of        C/S/S equipped with Medical Sensor SoC, optional wireless data        transmission, optional wireless energy harvesting and a monitor        that is suited for multimodal signals;    -   the use of a system combining biosignals and motor parameters        for patient monitoring;    -   the use of wireless sensor array data transmission for patient        monitoring;    -   the use of energy harvesting catheters, sheats, and shafts for        patient monitoring; and    -   the use of systems combining wireless medical sensor arrays for        patient monitoring.

BRIEF DESCRIPTION OF THE DRAWINGS

The medical invasive device according to the present invention, employedin connection with the method of computing cardiac output of a livingsubject according to the present invention, is described in more detailherein below by way of exemplary embodiments and with reference to theattached drawings, in which:

FIG. 1 is a cross-section of an embodiment of a medical invasive deviceaccording to the invention;

FIG. 2 is a side view of an embodiment of a medical invasive deviceaccording to the invention;

FIG. 3 represents an embodiment of a sheath with integrated flexibleelectronics board and receive coil circuit and an embodiment of a shaftwith integrated emitter coil circuit according to the invention; and

FIG. 4 is an embodiment of a sheath (outer element) covering a segmentof a shaft (inner element) in a coaxial orientation according to theinvention.

DETAILED DESCRIPTION

Sensor catheter: In one embodiment of a (C/S/S) according to the presentinvention, a standalone monitoring catheter was constructed by polymercasting, having 0.018″ inner lumen (intended for a guide wire) and anouter diameter of 2.8 mm, smaller than the sheath of current pulmonaryartery catheters. Contained in the polymer cast is a flexibleelectronics board from polymer with a diameter of 2.4 mm and a length of15 mm that connects the portion of the device inside the body with theportion outside the body. At its portion inside the body, the flexibleboard carries two digital sensors in one miniaturized package, namely adigital pressure sensor and a digital temperature sensor, withintegrated analog-to-digital conversion and a digital signaltransmission, packed into a single plastic body of 2*2*0.76 millimeters(STMicroelectronics, part Nr. LPS22HB), and at the portion outside thebody, the flexible electronics board carries a connector for wiredreadout.

Wireless sensor catheter: In one embodiment of a (C/S/S) according tothe present invention, a standalone monitoring catheter was constructedby polymer casting, having 0.018″ inner lumen (intended for a guidewire) and an outer diameter of 2.8 mm, smaller than the sheath ofcurrent pulmonary artery catheters. Contained in the polymer cast is aflexible electronics board from polymer with a diameter of 2.4 mm and alength of 15 mm that connects the portion of the device inside the bodywith the portion outside the body. At its portion inside the body, theflexible board carries two digital sensors in one miniaturized package,namely a digital pressure sensor and a digital temperature sensor, withintegrated analog-to-digital conversion and a digital signaltransmission, packed into a single plastic body of 2*2*0.76 millimeters(STMicroelectronics, part Nr. LPS22HB), and at the portion outside thebody, the flexible electronics board carries miniaturized chipscomprising digital communication and wireless transmission (TI) and asmall battery (type).

For successful energy harvesting, the energy harvested over time must besufficient to drive the sensors at the desired measurement intervals(typically ranging between 10 milliseconds to 4 hours) and to drivewireless transmission at its desired transmission intervals (typicallyranging between 100 milliseconds to 4 hours).

For inductive, wireless powering of the device, an externalelectromagnetic field needs to be built up. The requirements for thiselectromagnetic field include safety, capability for sufficient energytransfer, and compatibility with existing regulation. We have identifiedseveral design variants:

1) a custom designed energy receiving coil on a C/S/S and a matchedemitter coil with similar resonant frequency are constructed andoptimized such that the received energy is sufficient to drive theelectronics integrated in the C/S/S. An example of such a setup is shownin the examples. In a preferred setup, such a combination works in aradiofrequency band that legally permits medical use, and works with adistance from energy emitter to energy receiver that facilitates bedsideapplication, e.g. at 30-50 cm from the catheter insertion site.

2) an emitting field is created by an emitter in vicinity to the patientbed. Such energy transmission is well known in the field and is, forexample, described in detail in the ISO standard 15693 and performsenergy transmission and data transmission up to 1-1.5 meters. Anadvantage of this solution is that clinically desirable distance fromthe patient is maintained that simplifies patient care; a disadvantageof this solution is that the energy transmitted is low and typicallyallows only very limited functionality of the electronics on thereceiving device.

3) an emitting field is created by a transmitter put into proximity (upto 10 cm) of the exit site of the device in the skin. Transmission ofenergy and data is well known in the field and is described in detail inthe ISO standard 14443. An advantage of small distance is that theenergy yield at the receiver side is improved and thereby allows morefunctionality on the device side, and a disadvantage is that an emittercoil at this distance from the patient may hinder nursing care of apatient; also, this setup requires that the emitter coil remains insufficient proximity over time.

4) an emitting field is created by a transmitter according to a standardfor wireless charging, e.g. the Qi standard. The Qi standard isoriginally intended for high-current charging of devices like mobilephones in close proximity (centimeters) to the emitting coil, but wefound that a modified setup can be used that allows a larger distance(up to 1 m) to transfer smaller amounts of energy. While the amount ofenergy transferred is much smaller (decaying approximately with the cubeof the distance), this is still sufficient for the very low-powerelectronics used in our setup.

5) an emitting field is created by the catheter crossing asensor-equipped sheath. This scenario is preferred when thesensor-equipped sheath is used to guide the shaft of a circulatoryassist device into the body, thus assuring close proximity of emittingcoil and sensor-equipped device and optimizing energy transfer. Aworking example of this setup is given below.

Other upcoming standards for wireless interaction with transmission ofenergy and information, e.g. the EPC standard, differ in frequency band,data transmission protocols and other details but can be used whereverspecific requirements allow it.

In all options, higher frequencies typically facilitate the design ofemitter and receive coils because the desired resonance frequencies canbe achieved with lower inductances of coils and smaller capacitors.

Wireless energy transfer/harvesting: In a number of experiments, energyharvesting by coils integrated into our (C/S/S) was tested. To this end,a copper wire receive coil (200 micrometer copper wire, 25 windings,coil diameter 4 mm, coil length 85 mm, inductance estimated by resonanttuning 0.384 microhenry) was integrated into a sheath, cast in PDMS. Aresonant circuit was produced by connecting a 1 nanofarad capacitorparallel to the receive coil. Resonance in the receive circuit wasobserved at the frequency of 8.12 MHz.

In addition, an energy transmit coil was built from 200 micrometercopper wire, 30 windings, coil diameter of 2 mm and coil length of 150mm, having a measured inductance of 0.377 microhenry. The transmit coilwas placed into the shaft of a catheter-based cardiac assist device. Aresonant circuit was produced by connecting a capacitor of 1 nanofaradparallel to the emitter coil. Resonance in the emitter circuit wasobserved practically at the same resonance frequency (8.2 MHz) as in thereceive circuit. The shaft was inserted into the sheath so that theemitter coil was positioned coaxially in respect to the receive coil.The emitter circuit connected in serial to a 100 Ohm current-limitingresistor was driven by a sinusoidal signal with frequency of 8.12 MHzand amplitude of 10 V generated by a waveform generator Hewlett Packard33120A. The receive circuit was connected in serial to a diode TS4148used for rectification. The rectified signal was fed to a voltageregulator built based on LM3671 step-down DC-DC converter from TexasInstruments.

Successful energy transfer from the emitter circuit to the receivercircuit was documented as follows:

the voltage across a resistive load of 1 kOhm connected to the output ofthe voltage regulator was 3 V that corresponds to the current of 3 mAand the power of 9 mW. According to the specification of the pressureand temperature sensor LPS22HB and specification of Bluetooth Low Energy(LE) IC nrf52832 from Nordic Semiconductor this power is sufficient foracquisition of the pressure and temperature signals and transmission ofthe acquired data to a remote Bluetooth LE device.

These results confirm that sufficient energy can be transferred to theenergy harvesting, sensor carrying catheter.

Wireless energy transfer/harvesting: In one embodiment of a (C/S/S)according to the present invention, a copper wire receiver coil (200micrometer copper wire, 20 windings, coil diameter 5 mm, coil length 4mm, inductance estimated by resonant tuning 1.57 microhenry) wasintegrated into a sheath, cast in PDMS. A resonant circuit was producedby connecting a 100 picofarad capacitor parallel to the receive coil.Resonance in the receive circuit was observed at the frequency of 12.76MHz. The emitter coil was separate from the catheter and was implementedwith 200 micrometer copper wire, 2 windings, 88 mm coil diameter andcoil length 4 mm, having a measured inductance of 1.56 microhenry. Aresonant circuit was produced by connecting a 100 picofarad capacitorparallel to the emitter coil. Resonance in the emitter circuit wasobserved at 12.75 MHz. The emitter circuit connected in serial to a 1kOhm current-limiting resistor was driven by a sinusoidal signal withfrequency of 12.76 MHz and amplitude of 10 V generated by a waveformgenerator Hewlett Packard 33120A. An SMD1206 red LED was connected inparallel to the receive circuit. Successful energy transfer from theemitter circuit to the receiver circuit was documented as follows: whenthe emitter coil was positioned in proximity of the receive coil (at adistance of 1-3 mm) the LED started to shine indicating availability ofat least several hundred of microwatts of harvested electrical poweraccording to LED specification.

Wireless, energy harvesting sensor catheter: In one embodiment of a(C/S/S) according to the present invention, an access sheath for acatheter-based cardiac assist device was constructed by polymer casting,having an inner open lumen of 2.8 mm and an outer diameter of 4 mm,corresponding to the size requirements for access sheaths of the cardiacassist device. Contained in the polymer cast is a flexible electronicsboard from polymer with a diameter of 3 mm and a length of 15 mm thatconnects the portion of the device inside the body with the portionoutside the body. At its portion inside the body, the flexible boardcarries two digital sensors in one miniaturized package, namely adigital pressure sensor and a digital temperature sensor, withintegrated analog-to-digital conversion and a digital signaltransmission, packed into a single plastic body of 2*2*0.76 millimeters(STMicroelectronics, part Nr. LPS22HB), and at the portion outside thebody, the flexible electronics board carries miniaturized chipscomprising digital communication, wireless transmission and energyharvesting (TI).

The present disclosure also comprises the following further embodiments:

Embodiment 1 is a medical invasive device having a body portion arrangedto be inserted into one of, a blood vessel, a body cavity and a bodytissue, that is equipped with an electronic circuit and thatincorporates in the body portion a sensor arrangement and a digital datatransmission arrangement.

Embodiment 2 is the medical invasive device of embodiment 1, having ananalog-to-digital conversion arrangement in its body portion.

Embodiment 3 is the medical invasive device of the embodiment 1 or ofthe embodiment 2, wherein the medical invasive device has an outsideportion arranged to be positioned outside the body.

Embodiment 4 is the medical invasive device of any one of theembodiments 1 to 3, whereby the electronic circuit comprises a sensorarrangement having a temperature sensor, a pressure sensor, a vibrationsensor, an ultrasound sensor, a light sensor, a voltage sensor or anycombination thereof.

Embodiment 5 is the medical invasive device of any one of theembodiments 1 to 4, whereby the sensor arrangement comprises at leasttwo sensors for measurement of different physical signals.

Embodiment 6 is the medical invasive device of any one of theembodiments 1 to 5, whereby the sensor arrangement comprises at leastthree sensors for measurement of different physical signals.

Embodiment 7 is the medical invasive device of any one of theembodiments 1 to 6, wherein the medical invasive device has a shaftbeing an elongated object that carries the body portion and beingarranged to traverse the skin level.

Embodiment 8 is the medical invasive device of any one of theembodiments 1 to 7, wherein the medical invasive device is a catheterthat is an elongated object arranged to enter the body and comprises anumber of fluid columns.

Embodiment 9 is the medical invasive device of any one of theembodiments 1 to 8, wherein the medical invasive device is a sheath thatis an elongated object arranged to guide one of, a catheter, a shaft ofa therapeutic device, and a shaft of a heart pump.

Embodiment 10 is the medical invasive device of any one of theembodiments 1 to 9, wherein the body portion has a transversalcross-sectional area of less than 60 square millimetres.

Embodiment 11 is the medical invasive device of any one of theembodiments 1 to 10, wherein the body portion has a transversalcross-sectional area of less than 20 square millimetres.

Embodiment 12 is the medical invasive device of any one of theembodiments 1 to 11, wherein the body portion has a transversalcross-sectional area of less than 5 square millimetres.

Embodiment 13 is the medical invasive device of any one of theembodiments 1 to 12, whereby the electronic circuit comprises a wirelessdata transmission unit.

Embodiment 14 is the medical invasive device of any one of theembodiments 3 to 13, whereby the outside portion comprises a wirelessdata transmission unit.

Embodiment 15 is the medical invasive device of embodiment 14, wherebythe wireless data transmission unit is disconnectable from a base of theoutside portion.

Embodiment 16 is the medical invasive device of any one of theembodiments 1 to 15, powered by one of, a battery and a capacitor.

Embodiment 17 is the medical invasive device of any one of theembodiments 3 to 16, wherein a battery or a capacitor are disconnectablefrom the outside portion.

Embodiment 18 is the medical invasive device of any one of theembodiments 1 to 17, whereby the electronic circuit comprises aharvesting unit arranged to harvest energy from energy sources that arenot connected to the medical invasive device by wires.

Embodiment 19 is the medical invasive device of any one of theembodiments 3 to 18, whereby the outside portion carries a harvestingunit.

Embodiment 20 is the medical invasive device of embodiment 19, whereinthe harvesting unit comprises a coil for harvesting electromagneticenergy.

Embodiment 21 is the medical invasive device of any one of theembodiments 19 or 20, wherein the harvesting unit comprises a solarcell.

Embodiment 22 is the medical invasive device of any one of theembodiments 18 to 21, wherein the harvesting unit comprises avibration-based power generator.

Embodiment 23 is the medical invasive device of any one of theembodiments 18 to 22, wherein the harvesting unit comprises athermoelectric generator.

Embodiment 24 is the medical invasive device of any one of theembodiments 1 to 23, comprising a harvesting unit with a receiving coilcircuit that is tuned to a frequency such that an electromagnetic fieldtypically produced in its proximity elicits an energy transfer to thecoil that is sufficient to drive the electronic circuit on the bodyportion and optionally any other electronic circuits of the medicalinvasive device.

Embodiment 25 is the medical invasive device of any one of theembodiments 1 to 24, comprising a harvesting unit with a receiving coilcircuit arranged for energy harvesting from an electromagnetic field,whereby the field is produced by a number of emitting coil circuits, andwhereby an emitting coil circuit has a resonance frequency within 10% ofthe resonance frequency of the receive coil circuit, and preferablywithin 1% of the resonance frequency of the receive coil circuit, andparticularly preferably within 0.1% of the resonance frequency of thereceive coil circuit.

Embodiment 26 is the medical invasive device of any one of theembodiments 1 to 25, comprising a number of coil circuits arranged forenergy harvesting from an electromagnetic field in the frequency bandranging from 5.725 to 5.875 GHz.

Embodiment 27 is the medical invasive device of any one of theembodiments 1 to 26, comprising a number of coil circuits arranged forenergy harvesting from an electromagnetic field in the frequency bandranging from 2.4 to 2.5 GHz.

Embodiment 28 is the medical invasive device of any one of theembodiments 1 to 27, comprising a number of coil circuits arranged forenergy harvesting from an electromagnetic field in the frequency bandranging from 902 to 928 MHz.

Embodiment 29 is the medical invasive device according to any one of theembodiments 1 to 28, comprising a number of coil circuits arranged forenergy harvesting from an electromagnetic field in the frequency bandranging 13.553 to 13.567 MHz.

Embodiment 30 is the medical invasive device according to any one of theembodiments 1 to 29, comprising a number of coil circuits arranged forenergy harvesting from an electromagnetic field in the frequency bandranging from 6.765 to 6.795 MHz.

Embodiment 31 is the medical invasive device according to any one of theembodiments 1 to 30, comprising a number of coil circuits arranged forenergy harvesting from an electromagnetic field in the frequency bandranging from 235 to 275 kHz (Power Matters Alliance (PMA) defined band).

Embodiment 32 is the medical invasive device according to any one of theembodiments 1 to 31, comprising a number of coil circuits arranged forenergy harvesting from an electromagnetic field in the frequency bandranging from 110 to 205 kHz (Wireless Power Consortium (WPC) definedband).

Embodiment 33 is a kit comprising an outer element that is a sheathaccording to one of the embodiments 9 to 32, and an inner element beinga shaft or a catheter that comprises a coil circuit, whereby the outerelement covers at least a segment of the inner element.

Embodiment 34 is a kit according to embodiment 33, whereby the innerelement is arranged to be in a coaxial orientation relative to the outerelement.

Embodiment 35 is a kit according to embodiment 33 or 34, wherein aninner coil is arranged to transmit energy to the outer element.

Embodiment 36 is a kit according to embodiment 35, wherein the innercoil is arranged to receive data from the outer element by wirelesstransmission.

Embodiment 37 is a kit according to any one of embodiments 33 to 36,wherein an outer coil is arranged to receive data from the inner elementby wireless transmission.

Embodiment 38 is a kit according to any one of embodiments 33 to 37,wherein the inner element is the shaft of a percutaneous heart pump.

Embodiment 39 is a method of computing cardiac output (CO) of a livingsubject, wherein a mathematical model is constructed that links an inputdata vector with a target CO value.

Embodiment 40 is the method of embodiment 39, wherein said mathematicalmodel is nonlinear.

Embodiment 41 is the method of embodiments 39 or 40, wherein said inputdata vector comprises at least one sensor measurement acquired by amedical invasive device according to any of the embodiments 1 to 32.

Embodiment 42 is the method of any one of embodiments 39 to 41, whereinsaid input data vector comprises physiologic input source data from saidliving subject.

Embodiment 43 is the method of any one of embodiments 39 to 42, whereinsaid input data vector comprises the area under the curve of a repeatedtemperature measurement.

Embodiment 44 is the method of any one of embodiments 39 to 43, whereinsaid input data vector comprises the area under the curve of a repeatedtemperature measurement after injection of a bolus of fluid into thevenous circulation, whereby said injected bolus has a temperaturedifferent from the blood temperature.

Embodiment 45 is the method of any one of embodiments 39 to 44, whereinsaid input data vector comprises numbers derived from arterial pulsepressure analysis.

Embodiment 46 is the method of any one of embodiments 39 to 45, whereinsaid input data vector comprises numbers derived from arterial pulsepressure analysis, whereby said number is one of, beat-to-beat interval,beat rate, systolic pressure, diastolic pressure, pulse pressure, peaksystolic pressure difference per time difference, area under the pulsecurve and area under the systolic portion of a pulse pressure wave.

Embodiment 47 is the method of any one of embodiments 39 to 46, whereinsaid input data vector comprises at least one of: systolic pressure ofsaid living subject, diastolic pressure of said living subject, andpulse pressure of said living subject.

Embodiment 48 is the method of any one of embodiments 39 to 47, whereinsaid input data vector comprises at least one of: age of said livingsubject, gender of said living subject, height of said living subject,weight of said living subject, and temperature of said living subject.

Embodiment 49 is the method of any one of embodiments 39 to 48, whereinsaid input data vector comprises at least one of: cardiac pump type,cardiac pump performance setting, cardiac pump size, cardiac pump bloodflow, cardiac pump rotation speed, cardiac pump power consumption,cardiac pump electrical current consumption, cardiac pump pressuresensor reading.

Embodiment 50 is the method of any one of embodiments 39 to 49, whereinsaid target CO value is determined by an algorithm that comprisesdetermining the area under the curve of a temperature measuredrepeatedly at multiple time points.

Embodiment 51 is the method of any one of embodiments 39 to 50, whereinthe target CO value is determined by analysis of physiological signalsmeasured by a medical invasive device according to any of theembodiments 1 to 32.

Embodiment 52 is the method of any one of embodiments 39 to 51, wherebygenerating the mathematical model comprises fitting said input datavector into said target CO value in a least-square optimal fashion.

Embodiment 53 is the method of any one of embodiments 39 to 52, wherebygenerating the mathematical model comprises training of an artificialneural network (ANN).

Embodiment 54 is the method of any one of embodiments 39 to 53, wherebygenerating the mathematical model comprises unsupervised training of adeep neural network (DNN).

Embodiment 55 is the method of any one of embodiments 39 to 53, wherebygenerating the mathematical model comprises supervised training of adeep neural network (DNN).

Embodiment 56 is the method of any one of embodiments 39 to 55, wherebygenerating the mathematical model comprises training of a deep believenetwork (DBN).

Embodiment 57 is the method of any one of embodiments 39 to 56,comprising: obtaining an input data vector; transforming said input datavector using at least said mathematical model; and expressing a resultof said transformation as a CO value in physiologic units.

Embodiment 58 is the method of any one of embodiments 39 to 57,comprising: obtaining a plurality of said target CO values; generatingsaid mathematical model based at least in part on said target CO values;obtaining an input data vector; transforming said input data vectorusing at least said mathematical model; and expressing a result of saidtransformation as a CO value in physiologic units.

Embodiment 59 is an apparatus comprising an arrangement to receive datatransmitted by a medical invasive device according to any one of theembodiments 1 to 32.

Embodiment 60 is the apparatus of embodiment 59, wherein data arewirelessly transmitted by the medical invasive device.

Embodiment 61 is the apparatus of embodiment 59 or 60, comprising anarrangement to receive data, used for derivation of the input datavectors, transmitted from a second apparatus.

Embodiment 62 is the apparatus of embodiment 61, whereby the secondapparatus is a medical monitor, defined as a device that is arranged tobe placed in the same room as a patient and comprises a display arrangedto display vital signs of said patient.

Embodiment 63 is the apparatus of embodiment 61 or 62, whereby thesecond apparatus is the control device of a heart pump.

Embodiment 64 is the apparatus of any one of embodiments 61 to 63,comprising an arrangement to receive data, used for derivation of theinput data vectors, transmitted wirelessly from the second apparatus.

Embodiment 65 is the apparatus of any one of embodiments 60 to 64,whereby the wireless data transmission follows one of, the WiFistandard, the Bluetooth standard, the Ants standard.

Embodiment 66 is a computer program comprising a code structure arrangedto implement a method according to any one of embodiments 39 to 58 whenbeing executed on a computer.

Embodiment 67 is the apparatus according to any one of embodiments 59 to65, comprising a computer program according to the embodiment 66.

Embodiment 68 is the apparatus according to any of embodiments 59 to 65and to embodiment 67, comprising a display arranged to display at leastcardio output (CO).

Embodiment 69 is the computer program according to embodiment 66, storedon a computer readable medium.

Embodiment 70 is a computer program product stored on a machine readablecarrier, comprising program code means to implement a method accordingto any one of embodiments 39 to 58 when being executed on a computer.

1. A method of computing cardiac output (CO) of a living subject, wherein the method comprises constructing a mathematical model that links an input data vector with a target CO value.
 2. The method according to claim 1, wherein the mathematical model is nonlinear.
 3. The method according to claim 1, wherein the input data vector comprises at least one sensor measurement acquired by a medical invasive device, wherein the medical invasive device comprises an electronic circuit and a body portion, the body portion arranged to be inserted into one of a patient's blood vessel, a patient's body cavity, and a patient's body tissue, wherein the body portion incorporates a sensor arrangement and a digital data transmission arrangement.
 4. The method according to claim 1, wherein the input data vector comprises physiologic input source data from the living subject.
 5. The method according to claim 1, wherein the input data vector comprises an area under a curve of a repeated temperature measurement.
 6. The method according to claim 1, wherein the input data vector comprises an area under a curve of a repeated temperature measurement after injection of a bolus of fluid into a venous circulation, wherein the injected bolus has a temperature that is different from a blood temperature.
 7. The method according to claim 1, wherein the input data vector comprises numbers derived from arterial pulse pressure analysis.
 8. The method according to claim 1, wherein the input data vector comprises numbers derived from arterial pulse pressure analysis, wherein the number is one of beat-to-beat interval, beat rate, systolic pressure, diastolic pressure, pulse pressure, peak systolic pressure difference per time difference, area under a pulse curve, and area under a systolic portion of a pulse pressure wave.
 9. The method according to claim 1, wherein the input data vector comprises at least one of systolic pressure of the living subject, diastolic pressure of the living subject, and pulse pressure of the living subject.
 10. The method according to claim 1, wherein the input data vector comprises at least one of age of the living subject, gender of the living subject, height of the living subject, weight of the living subject, and temperature of the living subject.
 11. The method according to claim 1, wherein the input data vector comprises at least one of cardiac pump type, cardiac pump performance setting, cardiac pump size, cardiac pump blood flow, cardiac pump rotation speed, cardiac pump power consumption, cardiac pump electrical current consumption, and cardiac pump pressure sensor reading.
 12. The method according to claim 1, wherein the target CO value is determined by an algorithm that comprises determining an area under a curve of a temperature measured repeatedly at multiple time points.
 13. The method according to claim 1, wherein the target CO value is determined by analysis of physiological signals measured by a medical invasive device, wherein the medical invasive device comprises an electronic circuit and a body portion, the body portion arranged to be inserted into one of a patient's blood vessel, a patient's body cavity, and a patient's body tissue, wherein the body portion incorporates a sensor arrangement and a digital data transmission arrangement.
 14. The method according to claim 1, wherein generating the mathematical model comprises fitting the input data vector into the target CO value in a least-square optimal fashion.
 15. The method of claim 1, wherein constructing the mathematical model comprises training of an artificial neural network (ANN).
 16. The method of claim 1, wherein constructing the mathematical model comprises unsupervised training of a deep neural network (DNN).
 17. The method of claim 1, wherein constructing the mathematical model comprises supervised training of a deep neural network (DNN).
 18. The method of claim 1, wherein constructing the mathematical model comprises training of a deep believe network (DBN).
 19. The method according to claim 1, further comprising: obtaining an input data vector; transforming the input data vector using at least the mathematical model; and expressing a result of the transformation as a CO value in physiologic units.
 20. The method according to claim 1, further comprising: obtaining a plurality of target CO values; generating the mathematical model based at least in part on the target CO values; obtaining the input data vector; transforming the input data vector using at least the mathematical model; and expressing a result of the transformation as a CO value in physiologic units.
 21. A computer program comprising a code structure arranged to implement a method according to claim 1 when being executed on a computer.
 22. The computer program according to claim 21, stored on a computer readable medium.
 23. Computer program product stored on a machine-readable carrier, comprising program code means to implement a method according to claim 1 when being executed on a computer. 